What Does Parfocal Mean When Talking About Camera Lenses?

When talking about photography and photographic lenses a ‘parfocal’ lens is a zoom lens that maintains focus when the focal length of the lens is altered. The opposite of a parfocal lens is a ‘varifocal’ lens. Parfocal lenses are extremely convenient because they allow a photographer to quickly alter their perspective of a scene without having to refocus. The advent of autofocus lenses and digital cameras has somewhat overcome the problems caused by using varifocal lenses as camera software is able to quickly and automatically refocus an image when lens focal length is altered.